如何使我的存储变量可供所有类访问？ （UWP Windows.Storage，C＃）

Question

I am using ApplicationData.LocalSettings to save my variables between forms and for when the user closes and reopens the application. When I try to read the saved variables in another form, I need to insert the code into a method to use localSettings.Values ; otherwise, I get the error "A field initializer cannot reference the non-static field, method, or property FormName.localSettings":

Windows.Storage.ApplicationDataContainer localSettings = Windows.Storage.ApplicationData.Current.LocalSettings;
    Windows.Storage.StorageFolder localFolder = Windows.Storage.ApplicationData.Current.LocalFolder;

    Windows.Storage.ApplicationDataCompositeValue composite =
       (Windows.Storage.ApplicationDataCompositeValue)localSettings.Values["nutritionSettings"]; //this line brings the error

When I insert these lines of code into a method, it works, like this:

static void Storage()
    {
        Windows.Storage.ApplicationDataContainer localSettings = Windows.Storage.ApplicationData.Current.LocalSettings;
        Windows.Storage.StorageFolder localFolder = Windows.Storage.ApplicationData.Current.LocalFolder;

        Windows.Storage.ApplicationDataCompositeValue composite =
           (Windows.Storage.ApplicationDataCompositeValue)localSettings.Values["nutritionSettings"];
    }

However, I have not been able to figure out how to make the saved variables accessible outside of this method. Whenever I try to access them, I get the error, "The name 'composite' does not exist in this context':

 public LogFood()
    {
        this.InitializeComponent();


        int calorieMin = Convert.ToInt32(composite["calorieMin"]);
        int calorieMax = Convert.ToInt32(composite["calorieMax"]);
        int gramsFatMin = Convert.ToInt32(composite["gramsFatMin"]);
        int gramsFatMax = Convert.ToInt32(composite["gramsFatMax"]);
        int gramsCarbsMin = Convert.ToInt32(composite["gramsCarbsMin"]);
        int gramsCarbsMax = Convert.ToInt32(composite["gramsCarbsMax"]);
        int gramsProteinMin = Convert.ToInt32(composite["gramsProteinMin"]);
        int gramsProteinMax = Convert.ToInt32(composite["gramsProteinMax"]);

    }

What should I change about the method so that I can access these variables anywhere in the code for this form? I'm a bit new to C# as a whole, and methods as a whole tend to confuse me. Any recommended reading or documentation would be helpful.

Answer 1

"The name 'composite' does not exist in this context'

The problem is that you did not declare composite object in LogFood class. If you want to make variables accessible to all classes. You could declare public static in App class and John Wu is correct. For more please refer the following steps.

public static ApplicationDataCompositeValue composite;
public App()
{
    this.InitializeComponent();
    this.Suspending += OnSuspending;
    Windows.Storage.ApplicationDataContainer localSettings = Windows.Storage.ApplicationData.Current.LocalSettings;
    composite = (Windows.Storage.ApplicationDataCompositeValue)localSettings.Values["nutritionSettings"];
}

Usage

public LogFood()
{
    this.InitializeComponent();

    int calorieMin = Convert.ToInt32(App.composite["calorieMin"]);
}